A linear ball bearing as disclosed in EP-A1-0 080 515 is an integral part of a special guiding system. That bearing comprises a cuboid seating body which is open towards a linear body, such as a running rail, and which centrally houses a cylindrical runner body having semispherical ends. Two ball raceways, i.e. closed loops of loose balls, revolve in parallel planes on the runner body and engage the running rail at the open face of the seating body whose end walls are concave inside to accomodate the runner body ends.